diff --git a/purchase.py b/purchase.py
index 7743558cfb..38fc1673d2 100644
--- a/purchase.py
+++ b/purchase.py
@@ -708,7 +708,9 @@ class Purchase(Workflow, ModelSQL, ModelView, TaxableMixin):
             return
 
         invoice = self._get_invoice_purchase(invoice_type)
-        invoice.lines = list(chain.from_iterable(invoice_lines.itervalues()))
+        invoice.lines = list(chain.from_iterable(
+                invoice_lines[l.id] for l in self.lines
+                if l.id in invoice_lines))
         invoice.save()
 
         Invoice.update_taxes([invoice])